The present invention relates to a magnetic resonance imaging apparatus, and to a magnetic resonance imaging apparatus which transmits RF pulses to a subject in a magnetostatic space, performs an imaging sequence in which magnetic resonance signals generated by transmitting gradient pulses to the subject to which the RF pulses are transmitted are obtained as imaging data, and an image of the subject is generated on the basis of the imaging data obtained by the performance of the imaging sequence.
Magnetic resonance imaging (MRI) apparatuses are used in many different fields including medical and industrial purposes.
A magnetic resonance imaging apparatus excites spins of protons in a subject in a magnetostatic space by a nuclear magnetic resonance (NMR) phenomenon by irradiating the subject with an electromagnetic wave, and performs scanning to obtain magnetic resonance (MR) signals generated by the excited spins. And an image regarding the subject is generated from the magnetic resonance signals obtained by the scanning as raw data.
With a magnetic resonance imaging apparatus, blood vessel photography known as MRA (MR angiography) is performed for instance. As an MRA imaging method using no contrast medium, FBI (fresh blood imaging) is known (see Patent Document 1 for example). Other such methods include imaging methods utilizing the time of flight (TOF) effect or the phase contrast (PC) effect.    [Patent Document 1] Unexamined Japanese Patent Publication No. 2000-5144
By the FBI method, images are created regarding the imaging area in each of the diastole and the systole of the heart. And MRA images regarding the imaging area are obtained on the basis of the difference values between these images. Here, the signal intensity from the artery is lower in the systole because the blood stream velocity in the artery is faster and the signal intensity from the artery is higher in the diastole because the blood stream velocity in the artery is slower, with the result that the MRA images created on the basis of the difference values become more contrasty.
However, since a plurality of images are picked up at a plurality of timings and the MRA images are created by using the difference values between the images by the FBI method, if the subject moves its body in the course of imaging, body motion artifacts will arise significantly, and images may be blurred by T2 attenuation in the direction of phase encoding, possibly posing a difficulty to improve the quality of images.
In other imaging methods, in addition to the problem noted above, the imaging area is restricted, resulting in poor versatility.
These troubles would become especially conspicuous for the trunk and the lower thighs of the subject, because the artery and the vein run substantially parallel to each other and the T1 values and T2 values of the artery and the vein are close to each other.